ABSTRACT

UW CrB (MS1603.6+2600) was discovered during the Einstein Extended Medium Sensitivity Survey, and was optically identified with a 111 min eclipsing binary. Its nature remains unresolved: it is either an unusual low-mass X-ray binary (LMXB) or an unusual cataclysmic variable (CV). A ROSAT observation in the archive suggests a probable X-ray eclipse, but the low signal to noise ratio of the light curve prevents us from making a more definitive statement. Spectroscopy using the ROSAT data is also inconclusive in terms of the nature of this X-ray source. We request a 60 ks ASCA observation with which to investigate the eclipse in detail and to establish the shape of the X-ray spectrum, to be compared with those of known LMXBs and CVs of various sub-types.